fcn damm(digits){  // digits is something that supports an iterator of integers
   var [const]  tbl=Data(0,Int,		// 10x10 byte bucket
      0, 3, 1, 7, 5, 9, 8, 6, 4, 2,
      7, 0, 9, 2, 1, 5, 4, 8, 6, 3,
      4, 2, 0, 6, 8, 7, 1, 3, 5, 9,
      1, 7, 5, 0, 9, 8, 3, 4, 2, 6,
      6, 1, 2, 3, 0, 4, 5, 9, 7, 8,
      3, 6, 7, 4, 2, 0, 9, 5, 8, 1,
      5, 8, 6, 9, 7, 2, 0, 1, 3, 4,
      8, 9, 4, 5, 3, 6, 2, 0, 1, 7,
      9, 4, 3, 8, 6, 1, 7, 2, 0, 5,
      2, 5, 8, 1, 4, 3, 6, 7, 9, 0);
   0 == digits.reduce(fcn(interim,digit){ tbl[interim*10 + digit]  },0)
}